Answer:
 t = 6.6 10â»âž m
Explanation:
In this case we have that the reflection in the film is constructive, we take into account that
* When the light is reflected from the air (n = 1) to the film (n=2) it has a phase change of 180Âș
* within the film the wavelength is modulated by the index of refact
     λâ = λâ / n
taking into account these two aspects the expression for constructive interference is
     2n t = (m + œ)  λâ
let's find the minimum thickness (t) of the film
     t = (m + œ)  λâ / 2n
for m = 0
    t = œ  527 10â»âč /(2 2.00)
    t = 6.6 10â»âž m